I think it greatly varies by program, but generally there are a few people on the waiting list so the most important part is where you are ranked on the list. I was on the waiting list for Penn State's Social program last year but all applicants accepted their offers I was also on the waiting list for Depaul's social program but was eventually rejected.
This year I have been notified I am on the waiting list at 4 programs so far, although based on past experience I am not expecting much. I hope you have better luck than I did!